Gas exchange surfaces have a large surface area to increase the rate of diffusion. They're thin (one or two layers of squamous epithelium) to provide a short diffusion pathway across the exchange surface to increase the diffusion rate. The organism will maintain a steep concentration gradient of gases across he exchange surface.
There are 5 parts to the respiratory system:
1. Goblet cells, these secrete mucus. The mucus traps micro organisms to stop them reaching the alveoli.
2. Cilia on the surface 'beat' the mucus away from the alveolus towards the throat this prevents lung infections.
3. Elastic fibres…